I thought this was an urban legend that had been long put to bed - about landing light bulb life being relaed to the number of hours it is lit. Surely it was discovered long ago it is just a function of the number of airframe hours, as the aircraft vibration has far more of an impact on bulb life than for how long it is lit.
Possibly just an assumption about landing lights that has carried over from smaller aircraft that have more basic light designs and tend to fail a lot more often.